1. Field of the Disclosure
The present disclosure concerns a damper for a rotating part of a gas turbine engine.
2. Description of the Related Art
A gas turbine engine comprises various stages of rotor blades which rotate in use. Typically, a gas turbine engine would have at least one compressor rotor stage, and at least one turbine rotor stage.
There are a number of ways in which the blades of a rotor stage may be attached to the engine. Generally, the blades attach to a rotating component, such as a disc, that is linked to a rotating shaft. Conventionally, blades have been inserted and locked into slots formed in such discs.
Integral bladed disc rotors, also referred to as blisks (or bliscs), have also been proposed. Such blisks may be, for example, machined from a solid component, or may be manufactured by friction welding (for example linear friction welding) of the blades to the rim of the disc rotor.
Blisks have a number of advantages when compared with more traditional bladed disc rotor assemblies. For example, blisks are generally lighter than equivalent bladed disc assemblies in which the blades are inserted and locked into slots in the disc because traditional blade to disc mounting features, such as dovetail rim slots, blade roots, and locking features are no longer required. Blisks are therefore increasingly used in modern gas turbine engines, for example as part of the compressor section (including the fan of a turbofan engine).
Typically blisks are designed where possible to avoid vibration responses from, for example, resonance and flutter, which may be distortion driven. However, blisks lack inherent damping when compared to conventional bladed disc assemblies and resonances and flutter cannot always be avoided.
Additionally, the outer surface or rim of the blisk disc portion typically forms the inner annulus for working fluid in the gas turbine engine, such as at the compressor inlet. Thus the requirement for the inner annulus position fixes the blisk outer rim radius from the engine centre line thereby determining the basic size/shape of the disc portion. Accordingly, it may not be possible to design a blisk that avoids all forced vibration responses within such constraints.